Heat exchanging devices of this type, which are also referred to as finned coolers, are state of the art. With air as the cooling medium, such heat exchangers are often used for cooling hydraulic fluids for the working hydraulics of mechanical systems, such as construction machines or the like, for hydrostatic drive units or as oil coolers for heavily loaded gears, specifically in wind power stations. The document DE 10 2010 056 567 A1 discloses an example of the application of such a heat exchanger in a fluid/air cooling system to generate a cooling capacity for the hydraulic fluid in the hydraulic working circuit of an associated machine unit. During operation of such systems, the heat exchangers are subject to not only mechanical stresses, but they are also subject to thermal stresses in particular, due to the great range of temperatures that can arise at the system components during operation. Such stresses result both from the operating temperatures of the media involved, such as air and fluid, and from the influences of the ambient temperatures at the place of application of the heat exchangers, for example due to the climatic conditions at the place of application.
In the case of heat exchangers in the form of finned coolers with a conventional design that, as is revealed in DE 10 2010 046 913 A1, are made up of a bundle of plates lying on top of one another. Between the plates, duct-shaped air guides and fluid guides are alternately formed. For example, at high operating temperatures of the fluids resulting from swings in temperature of the type that occur in intermittent operation, stresses can occur in the bundle of components due to longitudinal expansion. Possible consequences include stress cracks in the bundle, which is joined together by soldering to form a rigid block, in particular in the region of the soldered seams. These stress cracks are accompanied by the danger of a malfunction of the heat exchanger, and thus, compromising the associated system. To avoid this danger, document DE 10 2010 046 913 A1 provides strips forming the soldering surfaces on the plates with a special profile shape, which leads to an approximately linear change in the bending strength of the shanks of the profile. An optimal bending behavior of the shanks is then obtained, and the risk of stress cracks at the soldering regions is minimized.
While the risk of interruption of operation in the case of swings in temperature over high temperature ranges is thus effectively avoided, problems can develop due to low temperatures arising at the heat exchanger. When corresponding systems are used in bitterly cold climatic zones, for example in northern areas of the USA, in Canada, Northern China or similar areas and when, in these applications, the systems are directly exposed to the environmental effects, for example, in the case of wind power stations, problems develop. The changes in viscosity of the fluid that occur at low temperatures during winter operation lead to pressure losses. Due to paraffin formation, which can take place in the fluids at low temperatures, a “freezing” of the heat exchanger can occur. To make fluid/air cooling systems suitable for winter, the heat exchangers concerned are conventionally designed with larger material thicknesses and/or the cooling air quantity is reduced by speed variance of the associated fan, for example, using control systems of the type described in DE 10 201 056 567 A1, cited above.